which Ralph E. Oesper of the University of Cincinnati has just sent to me and which he received under date of December 13, 1930, from Professor Le Chatelier, the latter states, "Je m'appelle Henry Louis Le Chatelier." My reasons for stating that he did not have a middle name were: 1. His signature; 2. The lack of a middle name in his published articles ; 3. The lack of a middle name on the official announcement of his death by his family; 4. The statement of his son, Fran~ois,that his name was Henry and not Henry Louis. ALEXANDER SILVERMAN UNIVER~ITY OF PITTSBUROE Pxrrs~uncn.PENNSYLVANIA
ISOTOPES AND ANALYTICAL STANDARDS To the Editor The discovery of many isotopes of the chemical elements has greatly increased the number of known atomic species. Probably the list is not yet complete, although a t present there are over two hundred fifty known. In spite of their number, isotopes have not affected appreciably the practical problems of the industrial analyst, since in nearly all cases the naturally occurring mixture for a given element seems to have a practically constant composition. The outstanding exception is lead, as it occurs in certain minerals. Baxter found that the element in one type has an atomic weight of 206 while that in another is 208. In these cases the use of the accepted value for ordinary lead (207.21) would lead to appreciable error in calculations. Also, evidence is accumulating that water from different sources may not have quite the same isotopic composition. While the analytical problem presented by isotopes still seems industrially unimportant, developments have reached the point that, in the interest of accuracy of statement, several fundamental definitions in freshman and analytical texts need revision. Of special importance is the discovery of three isotopes each of hydrogen and oxygen, the respective atomic weights being close to 1, 2, and 3, and 16, 17, and 18. Theobject of this note is to direct attention to the analytical significanceof these values with respect to atomic weights, equivalent weights, and the liter. Calculations involving masses of the elements are related ultimately to the value 16.0000, chosen arbitrarily as the atomic weight of oxygen. In most'texts it is not specified that this value refers to the naturally occurring mixture bf oxygen isotopes. If the proportion of
the three species, Ole, 01', and On, is known in the mixture, the atomic weights could be recalculated in terms of the lightest isotope. Since it predominates so largely in the mixture, the difference is not practically significant. However, the definition should be revised to conform to present practice. Equivalent weights present a similar situation. According to the common dehition, an equivalent weight is the mass chemically equivalent to 8.0000 g. of oxygen or 1.00 g. of hydrogen. Again, it should be indicated that these values refer to the commonly occurring mixture of the respective isotopes. In the definition of the liter the analyst also confronts the problem of isotopes. This standard of volume is related to the kilogram in being defined as the volume occupied by a mass of one kilogram of "pure" water a t the temperature of maximum density and under normal atmospheric pressure. With three isotopes eachof hydrogen and oxygen, it is obvious that the designation of "pure" water is not an adequate specification. The practical difficultiesinvolved in securingwater consisting of one isotope each of hydrogen and oxygen seem to preclude this possibility. Even though water from different sources shows slightly different densities, the only feasible procedke a t present for calibratin): volume& ware is to use ordin-ary water carefully a f i e d . The definition should then be changed to indicate that the liquid specified is composed of the naturally occurring mixture of the isotopes of the two elements. M. G. MELLON Punous UNIVERSITY LAFAYETTE, INDIANA
SOAP BUBBLES To the Editor DEARSIR: Apropos of the article "Tough Soap Films and Bubbles," by G. A. Cook,which appeared oa pages 161-6 of the April JOURNAL OF CHEMICAL EDUCATION, I wish to say that I have found that a solution of "Dreft" (a Procter and Gamble household product) carelessly made with either hard or soft water can be used with "raw" hydrogen directly from the generator to blow bubbles that can be successfully cut off and allowed to rise. It might be of interest to our readers to know this, and perhaps the author of the paper referred to might care to apply his tests to standardized solutions of "Dreft," or to even more concentrated forms of high molecular weight half-esters such as that used in "Dreft." FRANKB. WADE S K O R T R ~Hmn G E ScnooL INDIANAPOLI~, INDIANA
